dual carbs

[Guest Anonymous]

i read somewhere it's stupid to install dual carbs on a daily driver - any thoughts?

[Guest Anonymous]

If you find a set at the right price, or money is no object, it's worth a try. Sidedrafts acquired a bad reputation because people drive around with poor setups, and the car doesn't behave well. The original Solex PHH equipped TI supposedly had impeccable road manners.

If you come across a set of 40DCOEs or similar Mikunis, they would probably be less fussy on a street car than bigger 45DCOEs. I scored some vintage 45DCOEs from a 4-door TI, and it took me over a year of fiddling to get them to behave decently on my otherwise stock 2002. Once they were working OK, though, I didn't have to touch them again. I'll never go back to the downdraft setup. That intake manifold always seems to get in the way of something I want to do. Having sidedrafts gives you a lot more flexibility in tuning, they are modular and can be removed quickly.

If you're looking for gas mileage, they're probably not the best idea, though a good set can supposedly be tuned to give you decent mileage.

Mike

[Guest Anonymous]

I love my 40DCOEs... using a Schrick 292 cam and 9.5 pistons, ported head.

I set them up using an air/fuel ratio gauge.

Fortunately there was a good assortment of the various jets available to me at the time, it took a while to get the carbs sorted.

Mileage is not good (less than 20) but it's mostly my fault as I can't seem to keep my foot out of it.

It's a daily driver, started life as a '71 1600.

Extremely fun.

Scott

'71 1600/02ti

'71 2002/02tii

'73 shell, auto w/ sunroof project, at Dubois' (hi Michael).

[Guest Anonymous]

On my first 02 I went from the single Solex, to a single Weber ICH, to dual 45DCOEs, to a 320i fuel injection system.

With ANYTHING that was on the car, taking the time and money to set it up was paramount. a well tuned 34ICH will out perform poorly set DCOEs.

If I had to do it all over again and was determined to go sidedraught carbs, I would choose the 40s. The 45s were only really happy when you had the right foot down. Also, be aware that going to the DCOEs may take some engineering on your part to perfect the linkage. Lots of good solutions out there, shop around.

If it was mainly a daily driver car and didn't see much track/autocross time, I would probably opt for the 38/38. Well tuned, these are a major step up from the single solex.

The best advice is go drive some cars with the set up you are considering.

[Guest Anonymous]

or with mileage or driveability, but I think that 1 45 would do as well as 2 40's

[Guest Anonymous]

the progression holes are drilled into the carb, as indicated by the number after the bore, e.g. DCOE 40 18

I've heard it's important to get the right progressions, or idle and off- idle will be a bear- specifically, that Alfa- specific carbs don't really ever work right.

fwiw,

t

[Guest Anonymous]

I recently rebuilt my dual 45s and ran a single weber for about two

weeks. In my opinion, the car was just not the same. I remember

when I first did the conversion to duals ~4 years ago I was really

impressed. Putting the duals back on this time put a huge grin on

my face -- no comparison. That said, I like to *drive* my 02. If

you are looking for clean classic transportation, a single will work

fine. Also, go with a single carb unless you have modified your

engine (i.e high compression, big cam, tii dizzy, exhaust...), and

have them jetted by someone who knows there stuff (Ireland

Engineering did mine).

HTH,

Dewar

[Guest Anonymous]

I've never come across that claim. An Alpina-supplied setup 'back in the day' was one 45DCOE-15 and one 45DCOE-16; the numbers are different because the carbs were not identical, having different linkage setups from the factory for the 1-2 and 3-4 cylinders. Sure, the progression holes are placed by the factory, but the idle and progression circuits are controlled by the idle jet and related replaceable parts. I find it hard to believe that the characteristics of an Alfa motor are so different from a BMW motor that the carbs couldn't be set up to accomodate either. Slight changes in the camshaft and compression on either design will probably have far greater significance for the progression circuit than the overall design of the motor.

Mike

[Guest Anonymous]

My duel 40's side-draft set up was outstanding

performance wise, but when cold they cough and

sputter for a while. In the winter, it took several

minutes to get warmed up and running smoothly.

I would suggest buying them new and get

someone who knows what the hell they are doing

to install them.

The set up was about $1000+ which is quite an

investment. If you don't autocross your car or race

it, I would stick with a 2-bbl down draft for a daily

driver/driving around town car. Spend the money

on good tires and suspension.

[Guest Anonymous]

This solved the dead spot when you just come off of idle.

[Guest Anonymous]

after a anal rebuild (ouch) : )

along w/other mods (ignition etc) it ran like a scalded dog ... : )

Highly recommend them.

[Guest Anonymous]

It took awhile to hunt down someone who could really tune them right (Rebello Racing, Pacheco CA), but once the 40's were dialed in I've never been happier.My car's engine is a bone stock rebuild (+/-50,000miles now) with the exception of a Crane 3000 ignition, tii exhaust manifold, and the dual Mikuni set up.

They do have some cold weather starting quirks since the chokes were bypassed to improve long term reliability (Rebello's recommendation), but once I learned the nuances of starting them cold it's become a non-issue. (turn ignition on, let fuel pump run for a few secs, depress throttle fully three times about a sec each time, engage starter with throttle wide open...Fires right up everytime, every weather condition. 'the mikuni dance')

Now that my suspension upgrades are complete and the rest of the car is sorted to my liking (track car), it's time to finally start focusing on the engine...and really see what the dcoe's can do.

-s

[Guest Anonymous]

I know Alfa and BMW 2L 4 cyl engines are quite different. Alfa combustion chambers are hemi, with valves on opposite sides and the spark plug dead center. Alfa is twin cam, you can vary cam timing to alter open/close/overlap. Stock compression is 9:1, and IIRC the intake valves are a little bigger. I don't know all the numbers, but I know from owning both that the BMW 4 feels like it has more torque and makes its power earlier in the RPM range. The Alfa 4 makes all its go between 4500 and 7000, and makes more HP stock (about 130 hp). Of course, "stock" is a little hotter than a stock 2002 engine, since stock for the Alfa is twin cam, dual Dell'Ortos and a cast header. More like Tii output.

Tony

[Guest Anonymous]

thanks for the input everyone - dual 40/40 it is!

[Guest Anonymous]

You could choke 'em down if you've got a stock cam, etc. Email if interested.